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Old Jan 18, 2013, 01:35 AM
Mark Wood is offline
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Quote:
Originally Posted by oggamesta View Post
The advantages of a LiPo system are huge.
Such as?

mw
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Old Jan 18, 2013, 01:39 AM
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Quote:
Originally Posted by Mark Wood View Post
Such as?
They helped create a cottage industry for heavy duty fireproof bags with fancy Velcro closures?

Steve
Last edited by surfimp; Jan 18, 2013 at 01:39 AM. Reason: Trolling MW... it just never gets old
Old Jan 18, 2013, 05:27 AM
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Lol

BTW, the move to HV (high voltage) components such as servos and receivers is in response to a need to run unregulated LiFe packs. As they have a "native" voltage that is just slightly above nickel cells, they can be run as receiver packs where the components are "safe for higher voltages" without the addition of a voltage regulator. Apart from concerns about their use in fire-prone geographic areas, LiPo cells are too high in voltage for such usage, and need to be regulated when used as receiver packs.

Chris
Old Jan 18, 2013, 07:00 AM
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Just seen on ebay:
"787 battery packs - lightly used - ideal for barbeques"
Old Jan 18, 2013, 07:07 AM
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Quote:
Originally Posted by surfimp View Post
They helped create a cottage industry for heavy duty fireproof bags with fancy Velcro closures?

Steve
Ok. Besides that.

mw
Old Jan 18, 2013, 12:22 PM
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Quote:
Originally Posted by Woodstock 1 View Post
Lol

BTW, the move to HV (high voltage) components such as servos and receivers is in response to a need to run unregulated LiFe packs. As they have a "native" voltage that is just slightly above nickel cells, they can be run as receiver packs where the components are "safe for higher voltages" without the addition of a voltage regulator. Apart from concerns about their use in fire-prone geographic areas, LiPo cells are too high in voltage for such usage, and need to be regulated when used as receiver packs.

Chris
LiFe is rated at 6.6v
Looks to me like the goal is unregulated 2S LiPo 7.4v...at least with Futaba and Hitec.
Old Jan 18, 2013, 04:43 PM
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Quote:
Originally Posted by chris s View Post
Boeing has Lithium iron batteries ( LiFe) in the B787.C
Not sure if that's actually correct - checking on PPRUNE I found this from >thalesgroup< who supply some of the electronics for the 787
Quote:
Boeing has selected leading electrical power conversion technology from Thales ... Boeing chose Thalesís lithium-ion battery technology, which provides higher reliability and improved maintenance compared to traditional solutions, for the B787 low-voltage DC emergency back-up subsystem. This is a first in civil aviation...
... and will it be the last?
Old Jan 19, 2013, 01:54 AM
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Originally Posted by chris s View Post
You are right about the battery Steve, its a Lithium-ion-polymer. Don't know what the abbreviation for that is.
LiPo is a proper abbreviation.

Lithium Ion (Li-Ion) refers to the method in which they produce current, by the transfer of ions from the negative electrode, to the positive during discharge. Li-Ion does not refer to the chemistry which is used. Li-Po, LiFe etc. indicates chemistry, or the "type" of Li-Ion cell , they are still Li-Ion. There are several hundred Li-Ion chemistries, most are obscure and arent used in anything other than experimentation, or just too expensive to make, or no longer used or experimented with at all for some reason.
Old Jan 19, 2013, 02:44 AM
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Originally Posted by glasairIII View Post
...
Bottom line, Boeing will find the cause. And, I'd hazard a guess that they will temporarily go back to the tried and true nickel-cadmium. I'd also hazard a guess they went to the new technology for the same reason we do. Weight and capacity.
Boeing must find the cause and it must find a solution to avoid similar cases in future.

Going back to NiCd won't likely be possible, not only because of diminishing sources, but also because there is not enough space for batteries 4 times the size. The Boeing 787 is designed to use electric power, rather than bleed air:

http://www.boeing.com/commercial/aer...icle_04_3.html

http://www.boeing.com/commercial/aer...icle_02_2.html

Battery specs: http://www.gsyuasa-lp.com/aviation-lithium-ion-markets

Those were probably the best option back in 2005. Technology made massive steps since then, but it is not that simple to get batteries certified for use in aviation.

JŁrgen

P.S.: I am bit puzzled to find this discussion in the glider subforum.
Old Jan 19, 2013, 04:04 AM
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Originally Posted by Twyl View Post
Nor your Chevy Volt



That said, supposedly size does matter and a larger lipo will be more difficult to keep stable.

-Jonathan
I wonder how many cars have been incinerated due to gas (petrol) fires? ... an answer to the nearest 100,000 will do
Old Jan 19, 2013, 04:22 AM
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Ford Pinto anyone?
Old Jan 19, 2013, 07:00 AM
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Quote:
Originally Posted by snakecrew View Post
apparently 787's don't fair well either
Hey Snakecrew,

It seems like you posted this thread right after I did.

Here is my thread:
https://www.rcgroups.com/forums/show....php?t=1810901

Additionally, we really can not JUMP into any conclusions until the experts figure out what exactly happened to this Avionics box. You really can not compare it with any of our RC Hobby designs, setups and most especially Sail Plane setups.

Allow those who are investigating do their job.
Old Jan 19, 2013, 09:24 AM
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I'd be less concerned about Boeing's lithiums, and more concerned with all the lithium equipped wireless devices that passengers bring on board. Boeing will find a solution. I can't say the same for Joe Schmoe who just dropped his smartphone before coming on board.
Old Jan 19, 2013, 09:46 AM
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In an early electric plane, I had a ni-cad melt down. Ni-cad batteries were used because they had lower internal resistance than lead acid. Aircraft ni-cads requires a temperature monitoring gauge on the instrument panel to prevent thermal runaway. The maintenance required is very extensive also.
I do not know how many Volt cars have had fires in the wild. When crash testing one did burn up. 3 weeks after the test. They did not disconnect the battery as required by the manufacture. All other cars get the gas drained and battery disconnected right after the test. And remember that electrical fires destroy a lot of cars every year.
LiP batteries burn. So does gas and kerosene. About the only thing that does not ignite easily is glow fuel.
For sailplnes we can have a LiPo fire or a fire from a shorted, red hot wire, from any type of battery.
Ken
Old Jan 19, 2013, 09:49 AM
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Originally Posted by bjaffee View Post
Is anyone running LiFe packs in gliders? I've heard they don't require a regulator, and they are not as prone to fire as LiPos.
I'm only running LiFe in my sailplanes.


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